I have had problems when making backups. If I backup a course without course files and user files, everything works fine. I can of course make a zip of all the files in filemanager and then download it. Then I have separate file package but it doesn't take too much time to upload it to the new course. Message "backup can not be taken successfully" is what usually get, when I make a backup with all the files.
Hope this helps
Teemu